1. Field of the Invention
The present invention refers to a method and an electronic arrangement controlling the predetermined braking or deceleration, and particularly stoppage or detention, of motor driven mechanisms or moving bodies (mobiles).
More particularly, the present invention can be used for controlling the progressive braking of moving bodies or mechanisms i.e. mobiles, between certain points, in a minimum of operating time and with maximum efficiency, independently of initial, load and kinetic energy variations.
The present invention is applicable to uses such as controlling elevators, hoists, cranes, winches, transmission belts, electric motor driven vehicles, rolls or any other use in which it is required to precisely brake a mobile to reach a certain last point or position under certain conditions.
The present invention is specially applicable when the mobile is an elevator cabin, a crane boom, a transmission belt and in general, machine members which must efficiently translate between a plurality of positions, and stop precisely thereat.
The term "mobile" is used hereinafter to mean a vehicle or mechanism subjected to a certain movement between or through a set of points, positions or stations. The mobile is moved along a generally guided path, track or trajectory which includes at least one "control zone". This control zone is defined, in the present specification, as extending between a first or initial point and a destination, target or last point, inside which the mobile is controlled according to the present invention. It should be also understood that the movement referred to herein can be vertical, horizontal or oblique translation, rotation or combination of the same in relation to a certain mechanism.
2. Summary of the prior art
Electronic devices are progressively braking mobiles driven by electric motors and which must reach a certain speed and then attempt to smoothly stop in predetermined positions are known in the art. Such known arrangements requiere diverse types of elements such as electromechanical speed gauges and a series of mechanical, electromechanical, optical or magnetic sensors scaled along the movement path, to progressively send information referring to the relative position and speed of the mobiles. This progressive and variable information is transmitted through corresponding feedback loops that regulate the braking or deceleration energy applied to obtain the desired movement variations.
These arrangements are quite expensive due to the quantity, variety and type of their component elements, installation complexity, calibration and adjustment requirements, and for the same reason are prone to breakdowns, disadjustments or wear which call for frequent maintainance service.
In the known arrangements, the mobile speed is sensed, and as from a first point located a predetermined distance before the last point of the control zone, the sensed speed is compared at isochronal time intervals with a theoretical speed value predetermined as a time function, after which the necessary braking corrections are carried out. Consequently, these arrangements may not effect a constantly variable deceleration that assures the stoppage to occur exactly at the destination point. To overcome this problem, some time after braking is commenced and before the last point is reached, the mobile is progressibly slowed down to a minimum aproximation speed; after which it travels or "glides" more or less at this aproximation speed until it draws level with the destination (last) point where it activates the sensor which causes the mobile to be stopped. In this arrangement, this sensor is a must to indicate that the mobile has reached its final destination point.
The distance along which the mobile "glides" depends on the instantaneous work conditions, which in turn depend on the different loads and kinetic energy which must be neutralized. Consequently, considerable time is wasted when moving from one point to another, in particular due to the portion where the mobile "glides" at approximation speed. This is a distinct disadvantage in most cases which require faster speed of operation; i.e. minimum travel time, with maximum security and comfort factors.